The bolster of a railway freight car truck includes a centrally located ring which forms part of the pivotal connection between the truck and the car body. During service, the bolster ring may become severely worn or damaged, thereby rendering the bolster unfit for further use. In the past, worn rings were replaced by a burdensome procedure which entailed removing the bolster from the truck and mounting it on a large lathe so that the worn ring could be machined away. Thereafter, a replacement ring was placed on the machined surface, centered as best as possible by taking measurements to the mounting holes of the side bearing cages, and then welded in place manually. The particular ring renewal procedure with which we are acquainted required six hours.
The object of this invention is to provide an improved method and apparatus for replacing worn bolster rings. According to the invention, the new replacement technique employs a motorized circle cutting and welding machine which is automatically centered with respect to the bolster ring by supporting structure which engages mounting holes of the side bearing cages. The scheme utilize the two pairs of cage-mounting holes which are spaced from the ring center a uniform distance of 25" on nearly every freight car bolster now used by American railroads; therefore, careful design and fabrication of the supporting structure guarantees accuracy, eliminates the need for positioning adjustments, and enables ring replacement to be carried out on a routine basis. The worn ring is cut from the bolster using a torch driven by the motorized machine, thereby leaving a cut surface which lies in a plane parallel with the top surface of the bolster and which, except possibly for the hand removal of small slag deposits, requires no further dressing or trueing. After the worn ring is removed, the replacement ring is placed on the torch cut surface, centered automatically by a jig positioned by the motorized machine, tack welded to hold it in place, and then finish welded by a welding head driven around both the inner and outer peripheral surface of the ring by the motorized machine. The equipment required by the new replacement technique is portable, so removal of the bolster from the truck is not necessary. Furthermore, the entire ring replacement procedure may be carried out by one man in about an hour.